UEFI forum made it a requirement for motherboard constructors (hp, dell, msi...) to make their UEFI implementation to be able to at least read fat(12/16/32) filesystems. That is why you need a fat(12/16/32) partition flagged ESP (efi system partition) for holding your boot files.

So, I dont think you can do that unless you fall back to the old outdated BIOS or you have some *nix filesystem in your uefi implementation which I dont trust.